When a conventional commutator type motor with a series or shunt field winding, or a permanent-magnet field, is used in parallel with another motor and driven by a common circuit, it is difficult to balance the operating characteristics of the two motors, particularly in the case of series motors which have a high torque to running speed ratio. Nevertheless, balancing of the operating characteristics of such motors is often useful, for instance, when applied to an electric loader with unequal loads.